Target shields for improved magnetic properties of a recording medium

ABSTRACT

A collimator system is disclosed for use in an in-line pass-by sputtering system during the fabrication of recording media to improve the data storage density and read/write performance characteristics of the media. The collimator system includes a collimator shield and a collimator honeycomb. The shield includes a rectangular tube having a flange and a frame at inner and outer ends, respectively. The various components of the shield in part serve to prevent possible contamination of substrates due to target atom accumulation on the chamber walls during the sputtering process. The collimator honeycomb is provided for blocking target atoms from contacting the substrate at low incident angles. The collimator honeycomb is comprised of a plurality of collimators which are identical to each other. In a preferred embodiment, the collimators have a hexagonal cross-section taken from a perspective perpendicular to the substrate. The collimators may also have other geometric shapes. It is also contemplated that more than one collimator honeycomb level be used in alternative embodiments.

CLAIM OF PRIORITY

This application claims the benefit of U.S. Provisional Application No.60/088,330 filed on Jun. 4, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is generally related to the fabrication ofrecording media for use in hard disk drives, and in particular to acollimator system for use in an in-line pass-by sputtering system duringthe fabrication of recording media to improve the data storage densityand read/write performance characteristics of the media.

2. Description of Related Art

Thin film magnetic disks and disk drives are conventionally employed forstoring large amounts of data in magnetizable form. Data are writtenonto and read from a rapidly rotating recording disk by means of amagnetic head transducer assembly that flies closely over the surface ofthe disk. The escalating requirements for high areal recording densityin increasingly smaller disk drives impose increasing demands on thinfilm magnetic recording media in terms of signal modulation, coercivity(Hr), coercivity squareness (S′), signal-to-medium noise ratio (SMNR),and the sharpness of the output signal of the medium. Considerableeffort has been spent in recent years to produce magnetic recordingmedia having higher recording densities and satisfying such demandingrequirements, particularly for longitudinal recording.

Sputtering is a common process for depositing thin films onto substratesurfaces. The substrate (e.g., a glass-ceramic material) is typically aplanar disk that is positioned in a vertical pallet which passes througha sputtering chamber. This is called in-line pass-by sputtering. Aplanar target is positioned vertically within the chamber, and spacedapart in a counterfacing relation with the substrate. The target is madeof the material that is to be sputtered onto the substrate surface.

Examples of target material that are sputtered onto the substrate toform the recording media include chromium (Cr) or a Cr-containingunderlayer, a cobalt (Co) or Co-containing magnetic layer, and aprotective carbon (C) overcoat. There also may be a nickel aluminum(NiAl) seed layer between the underlayer and the substrate. The seedlayer, underlayer, magnetic layer and overcoat are typically depositedon the substrates in the sputtering system which contains sequentialdeposition chambers.

Referring to FIG. 1, fundamentally, sputtering involves bombarding thesurface of a target material 20 to be deposited as the film withelectrostatically accelerated argon ions. Generally, magnetic fields areused to trap electrons in a plasma gas, causing a dense concentration ofions to impinge on the target surface. As a result of momentum transfer,atoms (22, 24 and 32) are dislodged from the target surface in an areaknown as the erosion region. The dislodged particles follow a generallylinear trajectory from their point of emission on the target surface toa collision point on the juxtaposed surface of the substrate 26.Physical adhesion mechanisms cause the target particles to bond to thesurface of the substrate, thereby forming a film on the substrate. Inaddition to achieving high film deposition rates, sputtering offers theability to tailor film properties to a considerable extent.

It is extremely important in the fabrication of high density/highperformance magnetic disks that the process parameters be controlled toensure the deposited films exhibit the desired properties. However,typical sputtering systems of the type discussed above present certainproblems, in that the sputtered layers may show significant crystalanisotropy and/or variations in layer thickness. When the substrate ismoving in-line past a target, it is desirable that atoms impact thesubstrate at or near perpendicular to the surface of the substrate, suchas atom 22. However, it may happen that atoms are emitted that hit thesurface of the substrate at oblique angles, such as atom 24. Atoms whichrepeatedly hit the substrate at oblique angles may build upon previousatoms so that crystalline structures 28 (shown in FIG. 2) are formedthat create shadow effects on the substrate that cut off the depositionof atoms near the crystalline structures.

The formation of the crystalline structures, as well as non-uniformityof the deposited layers in general, creates several problems. Forexample, such crystalline growth can result in anisotropy in thedirection of disk travel through the in-line processes. Such anisotropyin the chromium underlayer and/or magnetic layer can significantlyreduce storage density and read/write performance of the finishedproduct. Anisotropy in the underlayer can disrupt the subsequentdeposition of the magnetic layer in the preferred orientation.Similarly, anisotropy within the magnetic layer, among other things, canlead to a variance and reduction of the coercivity in the magneticlayer. Coercivity is a measure of the magnetic energy necessary todemagnetize a medium from its remanent magnetic state. Moreover,variations in the thickness of the sputtered magnetic layer, as well asvariations in coercivity will also lead to signal modulation within therecording media. Signal modulation refers to variations in the signalreceived by the head during a read cycle.

Poor coercivity resulting from the formation of crystalline structuresand non-uniformity of the deposited magnetic layers also adverselyeffects signal sharpness and signal-to-medium noise ratio. A reversal ofpolarization between adjacent, oppositely magnetized segments on amedium cannot happen instantaneously. Signal sharpness is a measure ofhow quickly or sharply this reversal of polarization takes place. Lowercoercivities result in a slower and less sharp transition betweenoppositely magnetized segments, and consequently lower linear densities.Additionally, noise in magnetic recording media is greatest in thetransition region between adjacent, oppositely magnetized segments onthe media. Therefore, the large transition regions resulting from lowercoercivities also increases the noise in the media and degrades thesignal-to-media noise ratio.

One conventional method of controlling film deposition on the disksubstrate is to locate a shield 30 within the field between the targetand the substrates. The shield is preferably formed of a plurality ofsubstantially planar surfaces of minimal thickness in the shape of arectangular tube. With such an orientation, target atoms insubstantially perpendicular paths will reach the substrate withoutcontacting the shield, but target atoms (such as atom 32) travelingalong substantially oblique paths will contact the shield and will beblocked from reaching the substrate. α1 represents a smallest incidentangle possible employing the conventional shield.

Typically, α1 is approximately 28.5 degrees. It is however a problemwith the conventional shield that angles of incidence this low stillallow the formation of the crystalline structures, and does not preventnon-uniformity of the deposited layers in general.

It is also possible to enhance the magnetic properties of the media andreduce the modulation by circumferential scratching or employing a highargon pressure in the chamber. However, circumferential scratching cannot be used when a glass or glass-ceramic substrate is being used.Furthermore, while reducing the modulation, the high argon pressure alsoreduces the coercivity.

SUMMARY OF THE INVENTION

It is therefore an advantage of the present invention to provide amagnetic recording medium allowing improved storage density andperformance by exhibiting a low signal modulation, a high coercivity, ahigh coercivity squareness, a high signal-to-medium noise ratio, and ahigh sharpness of the output signal.

It is a further advantage of the present invention to provide acollimator system for use in a sputter apparatus that prevents atomsfrom the target from depositing on the substrate at low incident angles.

It is a still further advantage of the present invention to provide acollimator system for improving storage density and performance whichmay be easily incorporated into existing deposition shields.

These and other advantages are provided by the present invention, whichin a preferred embodiment relates to a collimator system for use in anin-line pass-by sputtering system during the fabrication of recordingmedia to improve the data storage density and read/write performancecharacteristics of the media. The collimator system includes acollimator shield and a collimator honeycomb. The shield includes arectangular tube having a flange and a frame at inner and outer ends,respectively. The various components of the shield in part serve toprevent possible contamination of substrates due to target atomaccumulation on the chamber walls during the sputtering process.

The collimator honeycomb is provided for blocking target atoms fromcontacting the substrate at low incident angles. The collimatorhoneycomb is comprised of a plurality of collimators which are identicalto each other. In a preferred embodiment, the collimators have ahexagonal cross-section taken from a perspective perpendicular to thesubstrate. The collimators may also have other geometric shapes. It isalso contemplated that more than one collimator honeycomb level be usedin alternative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to thedrawings, in which:

FIG. 1 is a cross-section view of a conventional shield used during thesputtering of thin films onto substrates;

FIG. 2 is an enlarged view showing the crystalline structures which formduring conventional sputtering processes;

FIG. 3 is a cross-section view of a collimator according to the presentinvention used during the sputtering of thin films onto substrates;

FIG. 4 is a cross-section view through line 4-4 in FIG. 3;

FIG. 5 is a chart comparing the coercivity (Hr) and coercivitysquareness (S′) of a substrate deposited with a conventional shield andthe collimator system according to the present invention;

FIG. 6 is a chart comparing the signal-to-medium noise ratio (SNMR) of asubstrate deposited with the conventional shield and the collimatorsystem according to the present invention;

FIG. 7 is a graph comparing the relative variation of the coercivityalong one track (dHr) of a substrate deposited with the conventionalshield and the collimator system according to the present invention;

FIG. 8 is a graph comparing the signal modulation of a substratedeposited with the conventional shield and the collimator systemaccording to the present invention;

FIG. 9 is a graph comparing the X-ray diffraction patterns ofglass-ceramic/CrV/CoCrPtTa films deposited with the conventional shieldand the collimator system for CoCrPtTa according to the presentinvention; and

FIG. 10 is a graph comparing the X-ray diffraction patterns ofglass-ceramic/NiPOx/NiAl/CrV/CoCrPtTa films deposited with theconventional shield and the collimator system for NiAl, CrV, andCoCrPtTa according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will now be described with reference to FIGS. 3 through10, which show a collimator system and characteristics of the collimatorsystem. The collimator system of the present invention shall bedescribed herein with regard to in-line pass-by PVD sputtering of thinfilms onto substrates to form recording media for hard disk drives.However, it is understood that the present invention may be used withstatic PVD sputtering, and deposition processes other than PVDsputtering.

Referring now to FIGS. 3 and 4, there is shown a collimator 100according to a preferred embodiment of the present invention locatedbetween a target 102 and glass-ceramic substrate 104. The substrate issecured in a vertical pallet which travels through an in-line pass-byPVD sputtering system. Although one collimator 100 is shown in FIGS. 3and 4, it is understood that a sputtering chamber may include two suchcollimators in front of two targets so that controlled deposition may beperformed on both sides of the substrate. It is contemplated that asputtering chamber include only one such collimator in alternativeembodiments. Moreover, it is understood that an in-line pass-bysputtering system may include a plurality of sputtering chambers forsputtering a plurality of layers onto the substrate. Each such chambermay include one or two collimators 100. An example of an in-line pass-bysputtering system in which the present invention may be used isdisclosed in U.S. Pat. No. 5,683,561, entitled “Apparatus and Method forHigh Throughput Sputtering”, which Patent is assigned to the owner ofthe present invention and which Patent is incorporated by referenceherein in its entirety.

FIGS. 3 and 4 cross-sectional views of the collimator 100, respectively.Although not critical to an understanding of the present invention, thetarget 102 and the substrate 104 are generally planar members orientedgenerally parallel to each other in a vertical x-z plane. The target isgenerally of a substantially rectangular shape having a heightcomparable in size to the pallet height. In one embodiment of theinvention, the target has a height of approximately 374 mm and a widthof approximately 91 mm. The substrate is generally a disk-shaped memberand secured in the pallet during the in-line pass-by PVD sputteringprocess. For a target having the dimensions described above, thesubstrate may have a diameter of approximately 130 mm and a thickness ofapproximately 1.27 mm. It is understood that both the shape and size ofthe substrates and target may vary in alternate embodiments of thepresent invention. It is also understood that the substrates and targetmay be formed of various materials. For example, the substrates may beformed of glass or glass-ceramic materials. The target may be formed ofvarious materials including for example, metals such as aluminum (Al),chromium (Cr), nickel (Ni), cobalt (Co) and alloys or compounds of thesematerials.

Emission-inducing energy is applied to an active face of the target inthe form of, for example, a plasma containing accelerated argon ions. Apower source (now shown) may be coupled to the target in order toprovide the source of the accelerated argon ions. As is known in theart, confinement magnets (not shown) may also be provided adjacent thetarget for trapping the electrons near the surface of the target, tothereby increase and more evenly distribute ion bombardment at thetarget.

As a result of the ion bombardment of the target, target atoms aredislodged from the target and travel linearly away from the target. Aspreviously described, it is desirable for those target atoms contactingthe surface of the substrate to travel along or near a substantiallyperpendicular path between the target and substrate. However, thedislodged target atoms typical travel away form the target along variousand random flight paths. As described in the Background of the Inventionsection, target atoms reaching the substrate at low incident anglesincrease the likelihood of crystal anisotropies, which in turn mayresult in low storage densities and poor read/write performance.

In order to prevent target atoms traveling along a substantially obliquepath from reaching the target, the collimator 100 according to thepresent invention intercepts atoms traveling from the target at lowincident angles. To ensure that the collimator 100 is effective over theheight of the pallet, the height of the collimator system is preferablylarger than that of the pallet. It is understood that the relative sizesof the collimator system and substrate may vary in alternate embodimentsprovided that the height of the collimator system is larger than theheight of the pallet. The collimator 100 may be used with pallets ofdifferent sizes. If it is used with large pallets, it is contemplatedthat several separate collimators, or a single collimator grid extendingthe length and width of the sputtering chamber wall, may be used.

During sputtering, target atoms are continuously deposited on theexposed surfaces of chamber walls in the sputtering system. After manypasses through the sputtering process, the accumulated target atoms onthe chamber walls will be released and contaminate substrates currentlypassing through the sputtering system. To avoid possible contaminationof substrates due to target atom accumulation on the chamber wallsduring the sputtering process, the collimator 100 includes a collimatorshield 106 as shown in FIG. 4. The collimator shield also supports acollimator honeycomb 108, as explained hereinafter.

The collimator shield 106 is formed as a series of panels 110 whichdefine a rectangular tube. The rectangular tube includes an inner end112 (nearest the substrate) which supports the collimator honeycomb 108,and an outer end 114 (nearest the target). Also located at the inner endis an outwardly extending flange 116 which is circumjacent about theinner end.

The outer end 114 of the rectangular tube includes a frame 118 definingan opening 120 therethrough for allowing the target atoms to passthrough during the sputtering process. The frame 118 functions to limitthe area of deposition of the target atoms. The shields also prevent theatoms from adjacent targets reaching on the substrate currently in frontof the target.

The collimator shield 106 is preferably made out of a metal such asstainless steel. It is understood that the collimator shield may also bemade of other materials, including aluminum, copper and titanium, inalternative embodiments. The particular material used depends upon thematerial being sputtered, and the adherence characteristics of thesputtered atoms. Moreover, the panels 110 of the rectangular tube, theflange 116 and the frame 118 should be substantially smooth in order toprovide minimum surface area and low oxidation levels. It is understoodthat the shield may be formed to other shapes in alternativeembodiments, such as square or circular shaped. The shape is preferablydetermined by the size and shape of the target. It is also understoodthat the collimator 100 may be formed without the flange and/or theframe in alternate embodiments.

As is further shown in FIGS. 3 and 4, the collimator honeycomb 108 isalso located at the inner end 112 of the collimator 100. In order toensure that the collimator honeycomb is effective over the entire heightof the pallet, the collimator honeycomb is preferably larger than theheight of the pallet and complements the shape of the collimator shield106. The collimator honeycomb 108 is comprised of a plurality ofcollimators 122 which are preferably identical to each other. In apreferred embodiment, the collimators 122 may be formed of a metal suchas stainless steel, but it is understood that the collimators 122 mayalso be made of other materials, including aluminum, copper andtitanium, in alternative embodiments.

As shown in FIG. 4, in an embodiment of the present invention, thecollimators have a hexagonal cross-section taken from a perspectiveperpendicular to the substrate. It is understood that the cross-sectionof the collimators may be other shapes, such as rectangular, triangular,octagonal or various other geometries. It is also understood that one ormore of the collimators 122 may have a dissimilar size and/orconfiguration than one or more other collimators 122. The collimatorsinclude walls which are substantially planar surfaces having minimalthickness. The walls are oriented perpendicular to the substrates on thepallet.

With such an orientation, particles traveling substantiallyperpendicular paths will reach the substrate without contacting thewalls of a collimator 122, but particles traveling along substantiallyoblique paths will contact the collimator walls and be blocked fromreaching the substrate. The minimum angle that a target atom may assumeupon leaving the target, and still contact the substrate is α2. In apreferred embodiment, α2 ranges between approximately 42° and 60° and ispreferably more than about 45°. It is understood that α2 may be above orbelow that range in alternative embodiments.

Up to this point, the collimator 100 has been described as including asingle level of collimator honeycombs 108. However, it is understoodthat the collimator 100 may include more than one collimator honeycomb108 such that one is positioned adjacent to and spaced apart from theother. In addition, the collimators of a first honeycomb may bestaggered with respect to the collimators of a second honeycomb (i.e.,one honeycomb level is shifted to the left or right and/or up or downwith respect to a second honeycomb level from the perspective shown inFIG. 4). It is further contemplated that first and second collimatorhoneycombs 108 may be staggered as described above, and also partiallycoplanar. That is, the staggered honeycombs also overlap so that thehoneycomb nearest the substrate has an outer bottom edge farther awayfrom the substrate than an inner top edge of the other honeycomb.

EXAMPLE

FIGS. 5 through 10 illustrate the comparison of magnetic properties andrecording performances of a substrate deposited with the collimator 100of the present invention on one side (Side A) of the substrate and aconventional shield on a second side (Side B) of the substrate.

In the example, a rigid magnetic recording substrate with identicaltargets on both sides of the substrate was deposited in an in-linepass-by PVD sputtering system. Both sides of the substrate weredeposited simultaneously.

As depicted in the charts, four kinds of film structures wereinvestigated and deposited with direct current (DC) magnetronsputtering. “CrV-Co-alloy” represents the medium with Co-alloy magneticlayer and CrV underlayer. “NiAl, CrV, & Co-alloy” represent the mediumwith Co-alloy magnetic layer, CrV underlayer, and NiAl seed layer.“NiPOx-CrV-Co-alloy” represents the medium with Co-alloy magnetic layerand CrV underlayer deposited on surface-oxidized NiP layer.“NiPOx-NiAl-CrV-Co-alloy” represents the medium with Co-alloy magneticlayer, CrV underlayer, and NiAl seed layer and deposited onsurface-oxidized NiP layer. The composition of the film structures inatomic percentage are shown in Table 1.

TABLE 1 Layer Nip NiAl CrV Co-alloy Composition 75% Ni, 50% Ni, 80% Cr,73% Co, 15% Cr, 25% P 50% Al 20% V 8% Pt, 4% Ta

The recording performances were tested with a Guzik 1601 read writeanalyzer. The Guzik 1601 was connected to a Guzik 1701 spin standemploying a magnetoresistive head operating at 4500 rotations per minute(rpm) and a recording density of 260 thousands of flux reversal per inch(KFCI).

The figures show that the remanent coercivity, remanent coercivitysquareness, and signal-to-medium noise ratio of the substrate depositedwith collimator 100 of the present invention are much higher than thoseof the substrate deposited with conventional shields. The modulation ofthe read-back signal, the relative variation of the remanent coercivity(dHr) and PW50 of such media deposited with the collimator 100 accordingto the present invention were also significantly reduced.

FIG. 9 depicts the X-ray diffraction patterns ofglass-ceramic/CrV/CoCrPtTa disk. FIG. 10 depicts the X-ray diffractionpatterns of glass-ceramic/CrV/CoCrPtTa disk. The patterns on the top ofFIGS. 9 and 10 were obtained from the substrate which was depositedusing conventional shields. The patterns on the bottom of the figureswere obtained from the substrate deposited using the collimator system.In FIG. 9, the collimator was used for CoCrPtTa deposition only. In FIG.10, the collimators were used for NiAl, CrV, and CoCrPtTa deposition.The undesirable Co (0002) crystallographic orientation of the media wassignificantly suppressed with use of the collimator 100. This is one ofthe reasons which accounts for a higher recording density and improvedread/write performance of a recording disk fabricated using thecollimator 100 according to the present invention.

Although the invention has been described in detail herein, it should beunderstood that the invention is not limited to the embodiments hereindisclosed. Various changes, substitutions and modifications may be madethereto by those skilled in the art without departing from the spirit orscope of the invention as described and defined by the appended claims.

What is claimed is:
 1. A collimator system used in an in-line, pass-bysputtering system for the manufacture of a recording medium of a diskdrive, the collimator system comprising: means for improving at leastone recording performance characteristic from a group of performancecharacteristics including signal modulation, coercivity, coercivitysquareness, signal-to-medium noise ratio and sharpness of output signal;and said means including a collimator shield and a collimator honeycombfor eliminating low incident deposition angles of particles which aredislodged from a target and emitted to a surface of a substrate.
 2. Acollimator system for improving magnetic properties of a recordingmedium in an in-line, pass-by sputtering system, the collimator systemcomprising: a collimator shield for reducing low incident depositionangles of particles which are dislodged from a target and emitted to asurface of a substrate; and a plurality of adjoined collimators forfurther reducing the low incident deposition angles; said collimatorshield and plurality of adjoined collimators improving at least one of asignal modulation, coercivity, coercivity squareness, signal-to-mediumnoise ratio and sharpness of output signal of the recording medium.
 3. Acollimator system as recited in claim 2, wherein said collimatorhoneycomb prevents particles from depositing on the recording medium atan incident angle lower than approximately 42°.
 4. A collimator systemas recited in claim 2, wherein a collimator of said plurality ofcollimators are honeycomb-shaped.
 5. A collimator system as recited inclaim 2, wherein a collimator of said plurality of collimators arerectangular-shaped.
 6. A collimator system as recited in claim 2,wherein a collimator of said plurality of collimators aretriangular-shaped.
 7. A collimator system as recited in claim 2, whereinsaid plurality of collimators comprise a first group of collimators anda second group of collimators, said first group of collimators beingcloser to the recording medium than said second group of collimators. 8.A collimator system used in an in-line, pass-by sputtering system forthe manufacture of a recording medium of a disk drive, the collimatorsystem comprising: a shield for reducing low incident deposition anglesof particles which are dislodged from a target and emitted to a surfaceof a substrate; and a plurality of adjoined collimators for furtherreducing the low incident deposition angles; said shield and pluralityof adjoined collimators improving a signal modulation, coercivity,coercivity squareness, signal-to-medium noise ratio and sharpness ofoutput signal of the recording medium.
 9. A collimator system as recitedin claim 8, wherein said collimator honeycomb prevents particles fromdepositing on the recording medium at an incident angle lower thanapproximately 42°.
 10. A collimator system as recited in claim 8,wherein a collimator of said plurality of collimators arehoneycomb-shaped.
 11. A collimator system as recited in claim 8, whereina collimator of said plurality of collimators are rectangular-shaped.12. A collimator system as recited in claim 8, wherein a collimator ofsaid plurality of collimators are triangular-shaped.
 13. A collimatorsystem as recited in claim 8, wherein said plurality of collimatorscomprise a first group of collimators and a second group of collimators,said first group of collimators being closer to the recording mediumthan said second group of collimators.